Rough, Unstable, or Incorrect Idle and Stalling

DEFINITION: The engine runs unevenly at idle. If bad enough, the vehicle may shake. Also, the idle may vary in rpm (called hunting). Either condition may be bad enough to cause stalling. Engine idles at incorrect speed.

Check:
^ Short term fuel trim values on Scan tool to check whether system is running rich or lean.
^ Carbon around throttle butterfly.
^ Generator charging output voltage. Repair if less than 13 volts or more than 16 volts with all accessories off.
^ Injectors clogged.
^ EVAP canister purge stuck open.
^ Intake leak between MAF and throttle body.
^ Fuel quality.
^ EGR valve stuck open.
^ ECM power and grounds.
^ Fuel pressure.
^ Spark plugs for arcing or corrosion.
^ Cylinder compression.